Vacuum type invebteb convebteb



June 15 1926.

1 w. cHuBB vAcUUu TYPE' INVERTED CONVERTER original Filed Nov. 29, 19154 sheets-Stien 1 v 7 AT'TORNEY June 15 1926.

L. W. CHUBB VACUUM TYPE INVERTED CONVERTER Qrginal Filed NOV. 29, 1915 4Sheets-Sheet 2 2 fvlllllilldltlfitil!!! lllllllllllll 1 f 1 A a I l I Il l n.

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INVENTOR BYLew/'.5' W. Chubb.

ATrRNEY VACUUM TY PE INVERTED CONVERTER y Origal Filed Nov. 29,v 1915 4Sheets-Sheet 4 1 A sneu o.onunu'o'o'auu'n 'l 1 58 6e y 6l 63 WITNEssEs;lNvENToRV /KJA M. Lewis wahl/bb.

g E Z BY 7 ATroRNl-:Y

named .im 15, 1926. 16,363

UNITED sTArEsPAT-ENT oFFlclaz.v

LEWIS W. CHUBB, F SWISSVALE, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSEELECTRIC AND MANUFACTURING COMPANY, A ORPOBATION 0l' PENNSYLVANIA.

vacuum TYPE mvna'riin conv-narnia. y

.25 employing a plurality Original No. 1,347,894, dated July 27, 1920,Serial No. 64,154, med November 89 1915. Application lfor reissue filedJune 11, 1921. Serial N0. 4?@,981 4 My invention relates to systems andapparatus for the conversion of direct currents into alternating.currents, and it has for its object to provlde devices of the characterdesignated which shall be simple and inexf .nsive in manufacture andhighly eEcctive 1n operation, being particularly adapted for theconversion of currents of high voltage.

' In the accompanying drawing, Fig. 1 is a l0 diagrammatic view of asystem of the character described that is adapted to formalternating-current waves in the load circuit having a u are-topformation; Fig. 2 is a. diagram il ustrating the wave form produced inthe system of Fig. 1; Fig. 3 is a diagram of .a system similar to thatshown in ig. 1 wherein means are rovided for approximating a sine-waveorm in the load circuit and, furthermore, wherein means-are 90 providedvfor varying the degree of electrostatic control; Fig. 4 is a diagramillustrating the wave form produced in the system of Fig. 3; Fig. 5 is adiagrammatic view of a device similar to that shown in Fig. 3 but ofcathodes of the incandescent type, with a thermal control of theelectronic emission; Fig. 6 is a diagram, similar to Fig. 4,illustrating the wave form produced in the system of Fig. 5; Fig. 7 is adiagrammatic view' of a system cmbodyin a vacuum'converter of the ureelectron- 1seharge type, together with a suppressor shield, for theelectrostatic control .of the arc, having novel characteristics, andFig. 8

isa view of the converter shown in Fig. 7 with the members thereofspaced apart to show the relative arrangement of the different componentparts.

In the operation of systemsof' electrical o distribution, itis'frequently desirable to convert energy from the form of directcurrent into alternating current. In the past, this function vhas beenperformed either by inverted rotary converters or b the use of "5 vacuumapparatus which has n more or less unsatisfactory in operation. In thedevelopment of aV system of high-voltage, direct-current transmission,it is necessary tha apparatus be provided lfor the conversion ofhigh-tension direct current into alternating current at the distributingend of the`line. inverted rotary converters are )unsuited for operationat high voltages on account of the. difficulties inherent to commutationand, so far 1s I know, no vacuum a paratus has as 1 yyet been developedwhich wi l operate at the voltages necessary for the economicaloperation of `a system of the character designated.

It is a Vwell known fact that'the arc`ows between the electrodes -in anevacuated contamer by virtue of a stream of electrons proeeding from4'the cathode and impinging upon the anode or anodes. By placing aconducting shield in roximit to an arc path of the character esignateand by imparting a negative charge to said conducting member, I amenabled to. seriously retard or prevent the ow of an electron stream ofthe character specified. In like manner, by imparting a positive char tosaid conducting shield, the passage of e ectrons to an anode isfacilitated.. It follows, therefore, that, by periodically impartingelectrostatic charges of various characteristics to said conductingshields, I am enabled to control, in a large measure, the production ofalternating current by a device of the character specified when suppliedwith direct current. It frequently becomesdesirable, or even' necessary,to aociate,with the alternating current consumption circuit, auxiliaryapparatus having a definite frequency, suc 'or example, as analternating-current generator or tuning apparatus, in order Vthat theremay be a natural agency 'operating in the alternating-current circuitfor determining the frequency thereof. By co-operation between thisfrequency-determining apparatus and the electrostatic control o supressor shields within the converter itself, am enabled -to produce anextremely efectivo control of the current ow.

I have found it convenient to apply, to ap aratus of the characterdesignated, the tite of Vacuum type inverted converter, 05

vacuum converter or rectierin the same manner as has hitherto beenemployed in distinguishin between the ordinary rotary converter an theinverted rotary converter, although it will be understood that myapparatus produces as'direct a conversion of Energy as is produced inthe ordinary rectier. l

I may employ vacuum apparatus of the mercury-vapor type, ,as commonlyemployed Y in the recti ation of alternatingcurrent or I may employ,l4with even better results, a paratus of the incandescent cathode typedisclosed, for-example, in U. S. Patent to. Fleming 803,684, or on page193 of the 1906 edition of a work entitled Conduction of electricitythrough gases by J. J. Thomson. The type of apparatus disclosed in thelast mentioned pu lcation produces exceptionally satisfactory results,as the pure electron emission employed readily subJects itself toelectrostatic control and as the electrodes are not subject todeterioration because of positive ,ionic bombardment.

There is no :fundamental di'erence between the o ration 'of a device ofthe character descri d by Fleming and a pure electron dischar device ofthe character described by homson. In the Fleming vdevice, the action isanalogous to that described on page 489 of the Thomson publication andmay be termed a step-by-step action, in that an electron proceeding fromthe cathode collides with a gas particle and disru ts the same, forminga new positive ion an a new electron. The original electron may lose alarge part of its energy and become inert but the newly formed electronproceeds toward the anode. This process may be repeated a reat number oftimes before an electron nally reaches the anode. The positive ions setfree by the disruption of the gas particles are drawn to the cathode andb their bombardment thereof produce new e ectrons therefrom. There isthus established what may be termed a reciprocal action, electronsproceeding from the cathode continuously generating positive ions fromthe residual gas and said positive ions in turn mg new electrons fromthe cathode itself. As the vacuum is carried to a'higher and higherdegree, the number of residual gas particles is reduced and the meanfree ath of electrons proceeding from the catho e is increased. Avcondition is soon reached wherein the voriginal electrons which startedfrom the cathode impinge upon the anode itself, and the 'state-Lof pureVelectron dis charge is ap roehed. By carrying the evacuations'tilfurther, `the number of gas particles is so reduced that substantiallyno positive-ions arefgenerated .within the device, and current'fiscarried 'entirely by electrous' proceedin directly from the-cathode tothe anode. 's is the method ofoperaproduci -bular members tion which isresent in a deviceof the character describes on page 193 of the Thomsonpublication. One of the most striking advanta s of the latter form of aparatus is e absence of positive ionic mbardment-of the cathode preventsthe ,deterioraltion of the latter and, consequentl tends to produce` adevice having long li e and extremely stable characteristics.

Referring to the accompanying drawing for a more detailed understandingof my invention, I show a container of the type commonly employed inmetal-case mercury converters at 9\1'n Fig. 1. The container' 9 isprovided with a pair of anodes 10 and 11 and with a cathode 12 of the vaorizable reconstructing type. ,Any suitab e means may be employed formaintaining the cath'- ode 12in an active condition, such, for example,as a keep-alive circuit 13. The anodes 10 and 11 are each provided withsup ressor shields 14 of the character descri ed and lclaimed in a coending application of S. W. Farnsworth, lerial No. 44,429, filed August9, 1915, Patent #1,232,470 July 3, 1917', and assigned to the Westinouse Electric & Manufacturing Company. rieliy described, the shields14-14 comprise casings 'l5-15 surrounding the anodes and provided withtransverse diaphragms 16-16 1n the lower portions thereof. Thediaphra-gms 16-16 supportconducting tubular members 17-17 throu h whichan arc from the cathode to the au'oe is forced to travel. The tubularmembers 17-17 are adapted to bev alternately connected and disconnectedfrom their respective anodes by means of a contact Vmaking' device 18which may be driven at any desired speed by a motor 19. The anodes 10and 11 are connected respectively to the terminals of the primarywinding 20 of a transformer 21, the secondar winding 22 of which isconnected to an a ternating-current consumption circuit 23, preferablyprovided with tuning devices, such, for example, as a condenser 24 and areactive coil 25. One terminal of a directcurrent supply circuit 26 isconnected to the mid point of the primary winding 20, and the otherterminal of said supply circuit is connected to the cathode 12 throughthe casing 9.

Having thus described the construction of a system embodying myinvention, the operation is as' follows: assuming the directcurrentcircuit 26 to be energized, with the contact-making device 18 in theostion shown, a stream of electrons is at li rty to pass from thecathode 12 to the anode 11 the tubular members 17 ofthe associatedshield 14 being maintained at positive polarit because of theirconnection to the an The formation of an are to said tuis prevented,however, by suitable' current-reducing means 27. Any

45, through rases attempt of an electron stream to pass to the f anode10, however, results in the rapid acquisition of a negative tential bythe tubular member 17 associated therewith, no I outlet being providedfor removing such 'a charge. ,The negative charge immediately exerts astrong repulsivev action and prefvents the supply of electrons to theanode 10.

Under the conditions above set forth, di-

10 rect 'current Hows from the system 26 through theright-hand half oftheprimary winding 20 and the anode 11vto the cathode 12, from whence itreturns to the system 26. A current wave is thereby induced in the l!secondarywinding 22 to ow through the -sysm 2a. When the contact-makingmember of the device 18 is turned through 90, the above 4describedconditions are reversed, the tubular membersl? associated with.the anodeare connected thereto, thus permitting current flowtherefrom, and thetubular members 17, associated with the anode 11,

acquire a negative char e, preventing the flow of current from saianode. There results a current wave in the left hand half of the primarywinding and a resultant impulse in the circuit 23 in the reversedirection from the first mentioned impulse.v

When operating at a reasonably high voltage and with large amounts ofmercury vapor within the apparatus, there is a strong tendency for anarc operating from an anode to persist after its shield is disconnectedand a condition of short circuit is established atJ the immediatelysubsequent energization of the shield of the remaining an- It may,therefore, be necessary, under the conditions above set forth, topositively choke out the flow of current from an anode at thetermination of the wave to be de-v rived therefrom-` and this may bestbe donc by producing an oscillating current flow said arc and causingsaid oscillating discharge to die down to a zero' value, as is disclosedand claimed in a copendin application of Chas. LeG. Fortescue, i erialo. 350,744, filed July 13, 1914, Patent #1,227,416, May 22, 1917, andassignedto the Westinghouse Electric & Manufacturing Company. v

Il ave found that, with an alternatingconsumption circuit having theorcharacteristics, it is diicult to operate a device of thecharacterspecified inthe manner shown, especially at high operating voltages,but, by causing the consumption circuit 23 to `have natural periodiccharacteristics,such,for example, as are provided by the tuningoperation of the devices 24 and 25 or by an auxiliary source-ofalternating current connected thereto, I am enabled to Vobtainsatisfactory operation. The action 06 of said auxiliary apparatus inproviding current electrostatic control of 'periodic points of zeropotential in they-circuit 23 is co-ordinated by driving the device 18 atthe proper speed and phase relationso that the connections of thetubular member 17 are 'altered contemporaneously therewith. 'l0

The operation of my device may be likcned, therefore, somewhat to theoperation of an ,asynchronous nerator in that it is necessary that the aternatin'.current systemA supplied thereby should ave, in itself,means-v for maintaining a periodic electromotive force for the properoperation of thc apparatus supplying current thereto.

he operation of the system shown in Fig. 1 in the manner described.produces 80 square-top (potential waves in the clrcuit 23, as indicateby a line 28-28 in Fig. 2. The derivation of a plurality of disconnectedand abruptly terminating impulses of f'ie character specified tends toset up surging and other undesirable phenomena 1n the circuit 26,especially when the latter is of con- -siderable length and of highvoltage. This .harmful result may be prevented by providing polyphase,vacuum-type converter 90 apparatus, Iwherein the net derivation ofenergy from the direct-current supply circuit is uniform, or, if it bedesired to employ singlehase apparatus, I may associate surgeampingapparatus with the system 26, such, for example, as the shuntincondensive devices 29 and the ser-ies in uctye devices 2929.

Referring now to the form of my invention shown in Fig. 3, I providemeans whereby the current wave supplied to the consumption circuit 23 iscaused to approxi'- kmate more closely to a sine Wave, thus'disturbingthe direct-current supply circuit to a lesser degree andv providingalternating current which permits more efficient operation ofelectromagnetic alternating-current apparatus. A container 30 isprovided with four anodes 31, 32, 33 and 34 associated, respectively,with tubular suppressing members 35k-35, 36-36, 37--37 and `3838. Acontact-making device 18 is provided for riodically connecting theanodes 31 to 34, inclusive, with their suppressor shields and comprisesfour equally spaced main conducting segments 39-39,`each of which isassociated with a pair of short conducting segments 40-40, one of whichlieson each side thereof. The pairs of short conducting segments areconnected together for thc/120 the anodes 31 and 34, whereas the mainsegments 39--39 arc employed for the electrostatic control of thesuppressing devices associated with' the anodes 32 and 33.

Not only may I connect the anodes 31 to 34, inclusive, to theirsuppressor shields through the instrun'lentalt-y of the device 18, but Imay connect all the suppressor shields to the cathode 12 through a.switch 41 in 130 order to more readily impart a ne tive charge theretoin the manner set fo and claimed in a -copending ap licatlon of'Chas.LeG. Fortescue, Serial o. 44,428 filed Au 9, l1915, Patent #1,231,587,.iuly s, 191 and assigned to the Westinghouse Electric da ManufacturingCompany.

In order that the alternating-current wave induced in the consumptioncircuit 23 may have a low value, as desired in the incipient st in theproduction of a sine wave, it isaeesirable that the primary windin 20include a large number of turns, so t at the ratio of transformation ofthe transformer 21 will be low in value and produce the desired lowvoltage from the circuit 26. If operating under ideal conditions, thenumber of active' turns in the primal member 20 should then be ra idlyreduce until the maximum desired vo tage is obtained in the secondarycircuit 23, whereupon the operation should be reversed and the number ofturns in the prim vwindin 20 should be increased, app ing infinit as alimit. In actual apparatus 1t is di cult to obtain even an aproxima-tion to the above described metho of operation because of theexpense incident to providing the large amount ofnecessaryya.ppa,ratus,.`l may obtain a crude `ap roximation'with the paratusshown in ig. 3 by connecting 31 and- 34 to the terminals of a priwinding 20 having a large number of turns and by connecting the anodes32 and 33 to intermediate symmetrically disposed points in said winding.

The operation, in a s stem of the character described, is as fo lows:Iassuming the conducting arm in the device 18 to turn in a'clockwisedirection, a pair of short-contact makingsegments 40-40 are firstconnected together, closing the circuit between the anode 31 and theassociated suppressing tubular member 35, and rmitting current flow fromsaid anode. K; impulse of direct current from the circuit 26 flowsthrough the entire left-hand half of the primary windin 20 and-producesa relatively low volta 1n the circuit 23, shown, for example, y a step42-42 in Fig. 4. Contact is next made between a pair of longcontact-making segments 394-39, charging the tubular members 36associated with the anode 32 permitting current flow therefrom andextinguishing the arc flowing from the anode 31, in the manner describedand claimed in U. S. patent to Percy H. Thomas, No. 945,006. The currentim ulse traverses only a small portion of the eft-hand half of therimary winding 20 and the resultant hig effective ratio oftransformation produces a high voltage in the secondar cuit 23, as shownby a line 43-43 in Fl, Contact is next made between another of segments40-40, and the tubular cir- 'g. 4. pair suP' e anodes pressor members35-35 an' again placed in connection with their associated anode 31,producing another low-voltage step in the wave of the circuit 23, shownby a line 45-45. The arc does no't readily transfer from the anode 32 tothe anode 31, in accordance with the disclosure in the above patentpreferring the better current path offered in the circuit of the anode32, and it is therefore desirable to oscillate the current to a zerovalue by the use 'of an auxiliary condenser or monocyclic square, asdisclosed in the above-mentioned application of Chas. LeG. Fortescue.Said current controlling apparatus forms no part ofthe present inventionand is omitted from the drawings for the sake of clearne. In alikemanner, the' arc must be forcibly extinguished at the anode 31 at theend of the active period.

The same cycle of o eration is now followed in connection wit the anodes33 `and 34 and the right hand half of the primary windin 20, thusproducing the negative half ofg an alternating-current cycle 1n thecircuit 23 as shown at 45 in Fig. 4.

It is seen that, by increasing the number of a'nodes in the container 30and so connecting said anodesas to increase the number of steps in theresultant current wave in the circuit 23, I may approximate a sine wave46-46 as closely as is warranted by the economic factors associated withthe design in question.

A`s above pointed out, the closure of the switch 41 permits a much morera id and complete negative electrification of t e tubular suppressormembers than would be possible were dependence placed solely upon theiracquisition of a n tive charge from the impact of a stream o electrons.I may, if desired, o a step further and so delicately adjust te size andrelation of the suppressor members as to permit current flow to an anodewhen its associated suppressor members are free and disconnected, and tochoke or suppress current flow when said suppreor members are placed inconnection with the cathode. Under such circumstances, thecontact-making device 18 would be inserted between the respectivesuppressor members and the cathode. A device of the character specifiedwould operate with less loss than would the system shown in Fig. 3,because there would be little or no energy loes such as is sEresent incurrent liow from the suppressor ield through a. resistance member to ananode, there bein solely an electrostatic charging and disc larging ofthe suppressormembers.

Referring now to the form of my invention shown in Fig. 5 wherein Iavail myself of the phenomenon that an electrode, when highly heated,tends to emit an excess of electrons, IA provide a highly evacuatedcontainer-47 with four cathodes 48, 49, 50 and 51 ofthelamentary I andwith an anode J 52. A' contact-making evice l18 is provided,

similar to that employed in Fig. 8, and is connected to send impulses ofheating current from a direct-current source 53 to the cathodes 48 to51, inclusive, inA succession.

The cathodes 48 to 51, inclusive, are con-U -nected to the primary`winding of the transformer 21 in the same manner as are the anodes 31-34in Fig. 3. The entire device 47 is highly exhausted and 'thoroughlytreated out as described in the Thompson publication above referred to,so that when one of the cathodes thereof is highly hea there results apure electron emission anda resultant flow of current from the, anode tothe cathode, u n the application of proper electromotive orce.

Assuming member of 'the contact makin the device 18 to rotate in aockwise direction as indicated, a circuit is first closed through thecathode 51, heating the latter to incandescence and permitting currentflow from a direct current supply circuit 26 to the anode 52, thence tothe cathode 51 and, via theentire left hand half of the primary winding2'0, to the source 26. There results an induced voltage in the circuit23 indicated by a step 54-54 in Fig. 6. Heating cunentis next suppliedto the cathode 50 and then reapplied to the cathode 51, roducing thesteps 55--55 and 56-56 1 in ig. 6 in the same manner as explained lylarge at length in connection with Figs. 3 and 4. In like manner, theenergization of the cathodes 48 and 49 then produces the negativehal1f157-,57 ofthe alternating-current wave in ig. 6. Y r

`When employing apparatus of the character described, it is notnecessary to oscillate the current to a zero value by the use ofauxiliary apparatus when it is desired to ex Y tinIguish the arc to anelectrode.

Y have found that, owing to the considerable mass of the cathodes 48 to51, inclusive, it is diiiicult to heat and cool the same with suilicientrapidity to reduce alternating current of commercial ucncies inthecircuit 23. Ima however, resort to the use of suppressor 'elds in apure electron-discharge device, as shown in Figs.7 and 8. An evacuatedcontainer 58 is provided with a relativefilmen cathode andwith fouranodes60, 61,'62 and 63v arranged adjacent thereto. The cathode 59 ismaintaned'in an electron-emitting condition by any suitable means, such,for example, as a source of heating current 64. Suppressor shields 65,66, 67 and 68, formed preferably of closely interwoven or intermeshedmasses of refractor wire, such, for example, as tungsten or mo ybdenum,are associated respectively with the anodes to 63, inclusive, andinterposed between said anodes and the cathode 59. A contact making'device 18 is employed to successively make contact between each anode.v4

and its attendant suppressor shield in the same manner as set forth inconnection with Fig. 3. The negative electron emission from the, cathode59 is therefore directed to each 'of the anodes in succession 'in suchuence as to produce the desired waveshape inthe circuit 23. p l a Itwill be understood that, in all cases, I maintain such 'inter-relationbetween the natural. frequenc of the circuit 23 and the` velocity of theevice 18 as to cause these two features to co-ordinate in the releaseand SuPPreion of ener iow from the direct-current supply circuit, so asto produce the desired operation.

Thron hout this description', I have explained t e action of my devicein accordance with the theory which seemsmos't lausible in view of thepresent knowledge o the underlying phenomena. I desire it to bedistinctly understood, however, that I do not conne myself to saidtheory` of operation but merely present the saine to aid in anunderstanding of the case.

While I have shown my invention in its preferred form, it will beobvious to those skilled in the art that it -is susceptible of variousminor changes and modifications without departing from the s iritthereof, and I desire, therefore, that-on y such limitations shall beplaced thereupon as are imposed by the -prior art or are the appendedclaims.

I claim as my invention: I

1. The combination with a direct-current supply circuit, of analternating-current consumption circuit, a vacuum-type invertedconverter interlinking said two circuits, and means'L associated withsaid converter for approximating a sine wave in the alternating currentproduced thereby.

2. The combination with a direct-current supply circuit, of analternating-current consumption circuit, a vacuum-type invertedconverter interlinkin .said two circuits, and means associated with saidconverter for producing a plurality of steps in the I.wave

orm of the alternating current' produced thereby, whereby a sine wavemay be approximated. v v

3. The combination with-a direct-current supply circuit, of analternating-current consumption circuit, a vacuum-'type invertvedconverter interlinking said two circuits, means for vtunin saidalternating-current circuit to the desired frequency, and meansassociated with the converter for responding to said uency and forexerting'a resultant contro ing action on the operation of'theconverter,

4. The combination with a direct-current supply circuit, of analternating-current consumglilon circuit, an inverted converter interling Said two circuits, and voltagespecifically set forth in adjusti-and-switching mechanisms dy- 5. The combination with a direct-currentmil supply circuit, of an alternating-current` consumption circuit, aninverted converter and ad ustable-ratio transformer interlinking twocircuits, and .switchin mechanism for va ing the ratio of saidtransformer, wherlelay theV voltage supplied to said consumption circuitmay be .periodically varied and an approximate sine wave ofelectromotive force impressed thereupon.

6. The combination with a direct-current supply stem, of analternating-current consumption circuit, a transformer having itssecondarywindin connected to said consumption circuit an having aplurality of voltage taps on its primary winding, aY vacuum-typeinverted converter comprisa plurality of electrodes of one nominalpuarity, at least one electrode of the opposite nominal polarit andelectron-controlling means interpose between the respective electrodesfor controlling current 'low therebetween, a connection from each ofsaid first named electrodes to one of said primary-voltage taps,respectivelyz and' switching mechanism arrangled to periodically andalternately energize t e electron-controlhng means associated withrelatively widely separated taps and relatively closely connected taps,whereby the electro-motive force supplied to said consumption circuit becaused to approximate a sine wave. The combination with a direct-currentsupply circuit, y of an alternating-current consumption circuit, amercury-arc inverted converter interlinking said two circuits, saidconverter embod in means for, ra idly changing its con uctivity from acon ition of low impedance to a condition-of high impedance, and viceversa, wherebysaid periods of changin y rief part of a cyc e, and tunedreactance means associated with said consumption circuit. l

8. The combination with a direct-current supply circuit, of analternating-current consumption circuit, a mercury-arc invertedconverter interlinking said two circuits, saidi converter embodyingmeans whereby the voltage of said converter suddenly rises to liighvalues, remains at such valuesfor an interval of time, and suddenly droto low values, and a tuned circuit coupl to said consumption circuit,whereb said tuned circuit carries substantially sinusoidal currents.

9. The combination with a direct-current conductivity occupy a c supplycircuit, of an alternating-current consumption circuit, a vacuum-tinverted converter interlinking said two circuits-and embodying anevacuated container provided with a pair of electrodes and with aconducting shield ad'acent the intervening current p ath, means ordeveloping an auxiliary periodic electromotive force in saidalternatingcurrent circuit, connectin means associated with saidconsumption circuit for controlling the potential of said shield andmeans for varying the connections of said connecting means.

' 10. The combination .with a direct-current supply circuit, of analternating-current consumption circuit, a vacuum-ty inverted converterinterlinking said two circuits and embodying an evacuated `containerrovided with a pair -of electrodes and wit ducting shield adjacent theintervening current path tuned reactance means associated with saiconsum tion circuit, connecting means associated with said consum tioncircuit for controlling the potentia of said shield and means forvarying the connections of said eonnectin means w nating current owingthrough said converter. may be controlled.

11. The combination with a direct-current supply circuit, of analternating-current consumption circuit, a vacuum-type invertedconverter interlinking said two circuits and including two electronfpaths and an anode and a shield for each o said electron paths, saidalternating-current consumption circuit including an inductance coilhaving its terminals connected to said anodes, one of the a conereby thealterterminals of lsaid direct-current circuit being connected to anintermediate point of said coil, the other terminal being connected tothe cathode Iterminals of said electron paths, means for developing anauxiliary periodic electromotive force in said-alternating-currentcircuit, connecting means associated with said consumption circuit forcontrolling ,the potentials of said shields and means forvarying theconnections of said connecting means.

12. The combination with a direct-current supply circuit, of analternating-current consumption circuit a vacuum-type inverted converterinterlinking said two circuits and including two electron paths andananode and a shield for each of said electron paths,

lll

said alternating-current consumption circuit/1l including an inductancecoil'having its terminals connected to said anodes, one of the terminalsof said direct-current circuit being connected to an intermediate pointof said coil, the other terminal being connected to the cathodeterminals of said electron paths, a tuned circuit coupled to said coil,connecting means associated with said consumption circuit forcontrolling the potentials of said shields and means for varying v maasthe connections of said connecting means whereby the alternatingcurrents flowing through said converter may be controlled.

13. The combination with a direct-current supply circuit, of analternating-current consumption circuit, a vacuum-type invertedconverter interlinking said two clrcuits and including a plurality ofelectron paths and a shield for each of said electron paths,tunedreactance means associated with said consumption circuit,connecting means associated with said consumption circuit forcontrolllng the potentials of said shields and meansl for varying theconnections of said connecting means whereby the alternating 15 currentsflowing through said converter maIy be controlled.

n testimony whereof, I have hereunto subscribed my name this 8th day' ofJune, 1921.

LEWIS W. CHUBB.

